Memo to Cubs: Don't trade Castro

The Cubs may be frustrated by Starlin Castro's on-field behavior but they'll love the player he's on pace to become. (Getty Images)

“We’re in a position where any opportunity to get better, any opportunity to improve our future is something that we have to take seriously, even if it means making difficult decisions about the product that we’re putting on the field right now.” That’s what Cubs president Theo Epstein told the Chicago Sun-Times’ Gordon Wittenmyer on Tuesday. Just one week earlier, Cubs manager Dale Sveum called a play on which Starlin Castro failed to turn an inning-ending double play because he forgot how many outs there were, “the last straw,” for his All-Star shortstop. Connect the dots between those two comments and one begins to wonder if the Cubs are looking to cash in Castro, who is their most valuable commodity but also arguably the best player in their entire organization.

If so, they should reconsider. Castro may be a frustrating player for Chicago's coaching staff -- he is prone to mental lapses like the one noted above and needs to, in Sveum’s words, “get his head in the game" -- but he’s also just a couple of months past his 22nd birthday and a career .304/.338/.425 hitter in 1,485 career major league plate appearances. Last week, I wrote about how one of the most remarkable and significant things about what 19-year-old Mike Trout and 20-year-old Bryce Harper are doing this season is their respective ages, and the same applies to Castro. Age is why the Cubs should be both more patient with his mental development and enthusiastic about his physical development.

There are a number of ways to illustrate this, but let’s start with the fact that last year, at the age of 21, Castro was worth 3.2 wins above replacement according to Baseball-Reference.com’s bWAR. In the entire history of the major leagues just eight other 21-year-old shortstops had more valuable seasons and every single one of them had long, productive major league careers. Four of the eight (if you include Alex Rodriguez) went on to become Hall of Fame players. In 2010, Castro posted a league-average 100 OPS+ while qualifying for the batting title as a 20-year-old shortstop. Only four men in history have posted a higher OPS+ under those conditions. Three of them went on to become Hall of Famers (again, including Rodriguez), and the last was John McGraw, who put up some Hall-worthy numbers as a third baseman in the 1890s before a knee injury made managing his top priority. In fact, there have been just 35 players at any position who have posted a league-average or better OPS+ while getting enough plate appearances to qualify for the batting title in their age-20 season and that list, again, is thick with stars and Hall of Famers.

The formula is simple: A player capable of being a competent major leaguer at 20 is one who has the talent to be a star at 25, a superstar at 27 and a Hall of Famer by their 50th birthday. That doesn’t mean it always works out, but Castro’s worst-case scenario, barring injury, is probably Garry Templeton’s career, which included 2,096 major league hits and was worth 24.9 wins above replacement. Yes, one of the best moves the Cardinals ever made was trading Templeton, but that was only because they got Ozzie Smith in return. Unless the Cubs can cash Castro in for a future first-ballot Hall of Famer at the same position and under the age of 30, they should hold on to him.